With the increasingly high cost of a college education, and a job market that appears anything but reassuring, there are plenty of reasons for young entrepreneurs to replace the expensive textbooks and cinder-block dorms for a business of their own.

Of course, starting your own company doesn't come without its own heavy costs. Though we certainly don't discourage students from pursuing any form of education, it's hard to imagine a life without Microsoft, Apple, Facebook or Tumblr.

Dropouts

1. David Karp, Tumblr

David Karp is best known for founding Tumblr. At the young age of 15, Karp dropped out of high school and began homeschooling. He never did get his diploma, but remains the CEO of Tumblr, which was acquired by Yahoo for $1.1 billion.

2. Ben Kaufman, Mophie

By his senior year of high school, Ben Kaufman had invented what started as an iPod charging accessory, called Mophie. The product won Best of Show at MacWorld 2006 -- the same year in which Kaufman briefly attended Champlain College, where he lists his activities as "not going to class."

He dropped out, and Mophie was acquired in 2007. Two years later, Kaufman went on to launch Quirky, a platform that allows inventors to submit their ideas. The inventions are critiqued and, if chosen, will be designed and manufactured by the Quirky team.

4. Kevin Rose, Digg

Kevin Rose attended the University of Nevada Las Vegas to major in computer science before dropping out in 1998. Rose worked for a few dot-com companies, and eventually helped co-found the news aggregation website Digg, which launched in 2004. The voting-style site has been credited to the precursor to other popular user-voting websites, such as Reddit.

5. Gabe Newell, Valve Corporation (Steam)

Gabe Newell is another Harvard dropout who worked at Microsoft for 13 years, then co-founded the gaming company Valve Corporation with Mike Harrington in 1996. Along with the Half-Life series, Valve is also known for creating Steam, a wildly popular digital gaming distribution network.

6. Bram Cohen, Bittorrent

After dropping out of SUNY Buffalo and working for several dot com companies throughout the '90s, Bram Cohen developed the peer-to-peer network Bittorrent. The idea came to him while working for MojoNation, a company that separates large encrypted files into smaller chunks on multiple computers. In order to download the file, a user would have to download separate pieces from many computers running the program. This inspired Cohen to apply the technology to P2P networks, like Kazaa, which gained a great deal of popularity at the time.

7. Mark Zuckerberg, Facebook

One of the most famous dropouts, Mark Zuckerberg created the popular social networking behmoth Facebook while studying psychology and computer science at Harvard. Zuckerberg dropped out in his sophomore year in order to work on the project full-time, and the rest is public history.

8. Bill Gates, Microsoft

Despite his disapproval of the term "dropout," Gates lasted at Harvard for three years. The Microsoft founder revealed in a Reddit AMA that he actually gained enough credits to graduate, but never followed through. In turn, Gates became one of the richest and most influential people in America.

9. Jake Nickell, Threadless

In 2000, Jake Nickell co-started Threadless with Jacob DeHart and just $1000. Two years later, he quit his former job and dropped out of art school to work full-time for the community based t-shirt company.

10. Michael Dell, Dell

Billionaire Michael Dell dropped out of University of Texas at just 19. Instead of studying biology, he spent most of his time in his dorm room, building computers and selling them through local newspapers. By the end of freshman year, he was raking in over $80,000 a month, so he dropped out of college to start the company that would eventually become Dell computers.

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